The present invention relates generally to electronic equipment and in particular the present invention relates to management of fan cooling for electronic equipment.
In high power density electronic systems, it frequently becomes necessary to use forced air-cooling to prevent equipment overheating. Heat sinks and electric fans are typically used to dissipate the heat generated by the electronic equipment. Some systems, such as telecommunication equipment, have maximum acoustic noise restrictions. These restrictions are primarily directed at the noise produced by the electric fan(s) used to cool the equipment. Often the cooling requirements and noise restrictions cannot all be satisfied simultaneously.
Further, open loop fan systems have a tendency to allow fans to run at higher speeds and power consumption levels, and voltage applied to the fans does not result in uniform fan speed even for tightly controlled voltages.
In an open loop multiple fan system, there can be substantial variation between fans as to how fast the fans operate when a voltage is applied to them. A commanded voltage is applied, amplified with a pulse width modulator, and applied to fans. In this type of system, because of tolerances on the fans, the fans do not run at identical speeds, even though the input voltage going into the fans is accurately controlled. There can be a noticeable speed difference between fans. If the fans are not operating at the same speed, then the fan operating at a faster speed actually may end up putting air in reverse through the slower turning fan, depending on how much speed difference there is. In a situation where one fan of a multiple fan system is beginning to wear out, and it is turning considerably slower than another fan, air can be forced backward through the failing fan.
Additionally, failure of cooling system components may interrupt service and is highly undesirable. Management of the system cooling, therefore, is necessary. For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a system and method of managing an electronic equipment cooling system, and for improved tolerances in managing fan operating speeds.
The above-mentioned problems with electronic equipment cooling systems and other problems are addressed by the present invention and will be understood by reading and studying the following specification.
In one embodiment, a fan control system includes a fan having a tachometer output signal indicative of actual fan speed, a fan power controller to generate a power signal to control a speed of the fan, and a feedback control module to adjust the speed of the fan to a desired speed given the actual fan speed.
In another embodiment, a closed loop fan control system includes a fan, a fan power controller connected to provide a power signal to the fan, and a feedback control module to adjust an operating speed of the fan to match a desired fan speed. The feedback control module includes a frequency to voltage converter to receive a tachometer output from the fan and to generate a signal representative of an actual fan speed, a speed error amplifier to receive the signal representative of actual fan speed and a speed control signal representative of a desired fan speed, and to generate a voltage control signal, and an output voltage error amplifier to receive the voltage control signal and a feedback signal from the fan power controller. The output voltage error amplifier generates a new control signal to the fan power controller.
In still another embodiment, an air-cooling system includes an electric fan, a control module coupled to adjust an operating speed of the electric fan based on a desired fan operating speed and an actual fan operating speed, and a feedback loop to provide a signal representative of actual fan operating speed and a fan power control signal to the control module.
In yet another embodiment, an air-cooling system including an electric fan has a control module coupled to adjust an operating speed of the electric fan based on a desired operating speed and an actual operating speed.
In still another embodiment, a method for controlling a fan operating speed includes generating a speed control signal indicative of a desired fan operating speed, feeding back a known fan operating speed to a speed error amplifier, generating a voltage control signal to adjust the known fan operating speed to the desired fan operating speed, and adjusting the actual fan operating speed with a fan power controller receiving the voltage control signal.
In yet another embodiment, a method for controlling the operation of a fan includes generating a speed control signal indicative of a desired fan speed, and applying the speed control signal and a feedback actual fan speed signal to a speed error amplifier. The speed control signal and the actual fan speed signal are compared in the speed error amplifier, a voltage control signal indicative of a desired adjustment to actual fan operating speed is generated, and the actual fan operating speed is adjusted to the desired fan speed.
Other embodiments are described and claimed